Features

GNUMail also uses an extensive number of bundles, some which are more mature than others. These can be disabled simply by either removing or changing their names such as
mv /usr/lib/GNUstep/ApplicationSupport/GNUMail/PGP.bundle/ ./PGP.bundle.hide

The Maildir message storage format should be preferred for new users (better performance, more robust).

If you are still using the mbox file format to store your messages and having problems try to delete the cache files. These can be found in your ~/Mailbox subdirectory.